Field of the Invention
The present invention relates to enzyme compositions, recombinant fungal host cells producing the enzyme compositions, and processes of producing and using the enzyme compositions.
Description of the Related Art
Lignocellulose, the world's largest renewable biomass resource, is composed mainly of lignin, cellulose, and hemicellulose. Cellulose is a polymer of glucose linked by beta-1,4-bonds known as beta-linked glucans. Hemicellulose is composed of xylans, which are polysaccharides formed from 1,4-β-glycoside-linked D-xylopyranoses.
Many microorganisms produce enzymes that hydrolyze the beta-linked glucans and xylans. Endoglucanases digest the cellulose polymer at random locations, opening it to attack by cellobiohydrolases. Cellobiohydrolases sequentially release molecules of cellobiose from the ends of the cellulose polymer. Cellobiose is a water-soluble beta-1,4-linked dimer of glucose. Beta-glucosidases hydrolyze cellobiose to glucose. Xylanases (e.g., endo-1,4-beta-xylanase, EC 3.2.1.8) hydrolyze internal β-1,4-xylosidic linkages in xylan to produce smaller molecular weight xylose and xylo-oligomers. Beta-xylosidases catalyze the exo-hydrolysis of short beta (1→4)-xylooligosaccharides to remove successive D-xylose residues from non-reducing termini.
The conversion of lignocellulosic feedstocks into ethanol has the advantages of the availability of large amounts of feedstock, the desirability of avoiding burning or land filling the materials, and the cleanliness of the ethanol fuel. Wood, agricultural residues, herbaceous crops, and municipal solid wastes have been considered as feedstocks for ethanol production. These materials primarily consist of cellulose, hemicellulose, and lignin. Once the cellulose is converted to glucose, the glucose is easily fermented by yeast into ethanol.
There is a need in the art for new enzyme compositions that can deconstruct cellulosic or hemicellulosic material more efficiently.
The present invention provides enzyme compositions and processes of producing and using the enzyme compositions.